Is Dolby Digital out the same as AC3?

Updated by Bryan Jones


This document helps answer questions about the Dolby Digital Plus family of codecs.


A customer asks, "On the Aero 100, is Dolby Digital out is the same as AC-3?"

The answer, in short, is yes. That is 100% correct.

For some more detail

Dolby Digital is actually a subset of the larger Dolby Digital Plus family of codecs. DD is AC-3, and DD+ is E-AC-3 (the “E” means “Enhanced”). The standard transmission codec in the U.S. is plain old AC-3. 

In some Linear products (like the latest AERO software versions) the menu and higher-level controls for Dolby actually say “Dolby Digital +”. This is because of a Dolby name change, requiring us to change it from the former “Dolby Digital” label. 

Technically speaking, the name change is correct, but it confuses customers at times; they see the DD+ menu and think their box doesn’t have regular DD when it really does. You need to open the DD+ menu and then choose “AC-3” as the codec type. 

If you look at the NfRemote configuration page for Dolby Digital Plus you will find the options.  These include the encoder type, Dolby Digital (DD) or Dolby Digital Plus (DD+) as well as the bit rate: 448 Kbs, 384 Kbs, 192Kbs. 

Some stations use 448 for 5.1 surround which provides the best quality.  Most use 384 for 5.1 surround as it leaves more bits for video encoding.  Stations encoding stereo only will use 192Kbs.

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